OPTIMIZATION OF DESIGN PARAMETERS FOR A CONTACT SENSOR IN BUMPER-PEDESTRIAN IMPACT BY USING FE MODELS

An active hood system was developed in Autoliv to minimize the head injury risk of pedestrians from impacts with car front. In order to detect the car-to-pedestrian impact in time, a contact sensor placed in the car bumper is needed. The stiffness of the bumper foam material is highly dependent on the environment temperature, which will result in unstable output from the contact sensor. A new pedestrian-bumper contact sensor was developed in Autoliv, in order to receive a stable output from the sensor at different temperatures. In this study, the new contact sensor was analyzed and evaluated by using a bumper FE model of a production car. A baseline bumper FE model was firstly developed and validated by using EuroNCAP lower legform impact tests on the production car bumper. In order to improve the safety performance of the bumper FE model, the bumper foam material was softened and the foam thickness was increased. At the same time, the location, boundary condition and material property of the lower stiffener was also adjusted. As a result, the improved bumper model can meet the acceptance requirements of the EEVC WG17 lower legform impact test. A human lower extremity FE model was developed and the safety performance of the improved bumper was further evaluated by using the human lower extremity FE model.